Michael Phelps Maths Problem

Michael Phelps Maths Problem Solution - 13 February

Michael Phelps , the famous swimmer can swim downstream in a lake in exact 40 minutes (with the lake current helping time).
He can swim upstream in a lake in exact 60 minutes (against the lake current).
The length of lake is 2 kilometers.

How long Michael Phelps can cover distance of one side at a still lake (no current).

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Solution
48 minutes.

Michael Phelps speed = X km/minute
Lake current speed = Y km/minute

2/(X+Y) = 402/(X-Y) = 60

Solving the simultaneous equations gives X = 1/24

Therefore, to cover 2km will take 2/X = 48 minutes